1. Field of the Invention
This invention relates in general to rotor aircraft, such as gyro planes, and in particular to the manual control systems, and more specifically to apparatus and methods for eliminating back drive in a push pull type system/assembly for a vehicle.
2. Description of the Related Art
Certain types of rotor wing aircraft such as gyro planes utilize, for example, a tiltrotor concept, which typically does not employ a swash plate to translate control inputs to the rotor disk and/or a hydraulic boost system. Rather, such flight control design directly manipulates the supporting rotor control head, itself, along both the pitch and roll axes.
During prerotation, the rotor of such a gyro plane is driven by a drive shaft that has a U-joint at either end. The U-joints are generally considered necessary, as the rotor must have freedom of movement to control the aircraft. However, when the U-joints are not perfectly aligned, this out of alignment condition creates a “kick” load that is fed into the flight control system and generally must be reacted by the controls. Ultimately, this “back drive” is felt, and must be reacted to, by the pilot using the control stick. Further, as the U-joints become more misaligned, the kick load amplitude can become so large that the flight control system becomes unstable. During a test of a recent prototype gyro plane, the pilot was able to maintain the stick in the proper position up to around 200 rpm, or 80% of the flight rpm. Above that rpm, the kick load amplitude became too large for the pilot to maintain the control stick in a stable position. Accordingly, recognized by the inventors is the need for an apparatus and methods for eliminating uncontrollable back drive in a flight control or other type of similarly configured machine//vehicle control system.
Similarly, during cruise flight, at some advance ratio (aircraft speed/rotor tip speed), the rotor will become unstable. Accordingly, further recognized is the need for an apparatus and methods that allow the pilot to maintain control of the rotor even when the rotor system is unstable during cruise flight.